1. Field of the Invention
The present invention relates generally to the packaging of electronic components. More particularly, the present invention relates to a laser module and optical subassembly and method of fabricating the same.
2. Description of the Related Art
Laser diodes, e.g., semiconductor lasers, were used in laser modules. These laser modules were used in a wide variety of applications such as in high-performance optical networks.
Conventionally, the power output from the laser diode had to fall within fairly broad limits. Variations in the power output from laser diode to laser diode was acceptable as long as the power output fell within the broad limits. However, newer applications required the power output of each individual laser diode to fall within tight tolerance limits.
As is well known to those of skill in the art, a laser diode emitted light from both a front facet and a back facet. Typically, most of the power output from the laser diode was from the front facet, e.g., 98% or greater. The light from the front faucet was coupled to an optical fiber for transmission.
Conversely, only a small amount of the power output from the laser diode was from the back facet, e.g., 2% or less. However, the power output from the back facet directly varied with the power output from the front facet. Thus, by monitoring the light from the back facet, the power output from the front facet could also be monitored. The light from the back facet was monitored by a photodiode.
To allow the photodiode to monitor the light from the back facet accurately and repeatably, the photodiode and the laser diode had to be precisely aligned. In addition, heat generated by the laser diode and the photodiode had to be efficiently removed to prevent overheating and defective operation of the laser diode and the photodiode. Further, it was important that this alignment and cooling was achieved at a low cost.
In accordance with one embodiment of the present invention, a laser module includes an alignment plate having a template plate having a laser diode aperture and a photodiode aperture. A weld plate and a reflector are coupled to the template plate. The laser module further includes a heat sink coupled to the alignment plate. A photodiode subassembly is mounted within the photodiode aperture and to the heat sink. Further, a laser diode subassembly is mounted within the laser diode aperture and to the heat sink.
By mounting the photodiode subassembly and the laser diode subassembly within the laser diode aperture and the photodiode aperture, respectively, the photodiode subassembly and the laser diode subassembly are inherently aligned to one another and also to the reflector.
Further, by mounting the photodiode subassembly and the laser diode subassembly directly to the heat sink, heat transfer efficiency from the photodiode subassembly and the laser diode subassembly to the heat sink is improved compared to having the heat conducted additionally through the alignment plate. This insures that a photodiode of the photodiode subassembly and a laser diode of the laser diode subassembly are not overheated.
The present invention is best understood by reference to the following detailed description when read in conjunction with the accompanying drawings.